title: Charge-based detection of small molecules by plasmonic-based electrochemical impedance microscopy.
abstract: Charge-based detection of small molecules is demonstrated by plasmonic-based electrochemical impedance microscopy (P-EIM). The dependence of surface plasmon resonance (SPR) on surface charge density is used to detect small molecules (60-120 Da) printed on a dextran-modified sensor surface. Local variations in charge density on an electrode surface are manifest in an optical SPR signal. The SPR response to an applied ac potential measures the sensor surface impedance which is a function of the surface charge density. This optical signal is comprised of a dc and an ac component, and is measured with high spatial resolution. The dc element of the SPR signal represents conventional SPR imaging information. The amplitude and phase of local surface impedance is provided by the ac component. The phase signal of the small molecules is a function of their charge status, which is manipulated by the pH of a solution. Small molecules with positive, neutral, and negative charge are detected by P-EIM. This technique is used to detect and distinguish small molecules based on their charge status, thereby circumventing the mass limitation (~100 Da) of conventional SPR measurement.
authors.affiliation: School of Electrical, Computer, and Energy Engineering, Arizona State University, Tempe, Arizona 85287, United States.
authors.forename: Christopher
authors.initials: C
authors.lastname: MacGriff
authors.forename: Shaopeng
authors.initials: S
authors.lastname: Wang
authors.forename: Peter
authors.initials: P
authors.lastname: Wiktor
authors.forename: Wei
authors.initials: W
authors.lastname: Wang
authors.forename: Xiaonan
authors.initials: X
authors.lastname: Shan
authors.forename: Nongjian
authors.initials: N
authors.lastname: Tao
mesh_terms: D015374:Biosensing Techniques / Q000379:methods*; D017097:Electric Impedance; D055664:Electrochemical Techniques / Q000379:methods*; D008853:Microscopy / Q000379:methods; D020349:Surface Plasmon Resonance / Q000379:methods*